This paper deals with a clustering approach for VANETs operating in sparse highway scenarios. The proposed protocol is able to keep high and stable the network connectivity level to allow data exchange among nodes and, thus, achieving context awareness. The criterion adopted in forming a cluster involves the periodic distributed evaluation of connectivity indicators combining the number of neighbors and their distances, without excessive signaling overhead. In this way, data propagation leverages on vehicles physical movements instead of setting up a communications backbone, which cannot properly face a high mobility level. The performance has been analyzed in a practical scenario adopting IEEE 802.11p communications standard.